Effects of experience and commercialisation on survival in Himalayan mountaineering: retrospective cohort study.

OBJECTIVES: To determine whether previous Himalayan experience is associated with a decreased risk of climbing death, and whether mountaineers participating in commercial expeditions differ in their risk of death relative to those participating in traditional climbs. DESIGN: Retrospective cohort study. SETTING: Expeditions in the Nepalese Himalayan peaks, from 1 January 1970 to the spring climbing season in 2010. PARTICIPANTS: 23,995 non-porters venturing above base camp on 39,038 climbs, 23,295 on 8000 m peaks. OUTCOME: Death. RESULTS: After controlling for use of standard route, peak, age, season, sex, summit success, and year of expedition, increased Himalayan experience was not associated with a change in the odds of death (odds ratio 1.00, 95% confidence interval 0.96 to 1.05, P = 0.904). Participation in a commercial climb was associated with a 37% lower odds of death relative to a traditional venture, although not significantly (0.63, 0.37 to 1.09, P = 0.100). Choice of peak was clearly associated with altered odds of death (omnibus P<0.001); year of expedition was associated with a significant trend toward reduced odds of death (0.98, 0.96 to 0.99, P = 0.011). CONCLUSIONS: No net survival benefit is associated with increased Himalayan experience or participation in a traditional (versus commercial) venture. The incremental decrease in risk associated with calendar year suggests that cumulative, collective knowledge and general innovation are more important than individual experience in improving the odds of survival.